1. Field of the Invention
The present invention relates to a control circuit applied to a power converter and an operation method thereof, and particularly to a control circuit and an operation method thereof that can simultaneously realize a brown-out protection, an over-temperature protection, and an over-voltage protection.
2. Description of the Prior Art
In the prior art, a control circuit applied to a power converter integrates a brown-out protection and an over-temperature protection into the same pin, and a current sensing pin detects an output voltage of a secondary side of the power converter through an auxiliary winding of the power converter to execute an over-voltage protection when a power switch of the power converter is turned off.
In the prior art, the control circuit executes the over-temperature protection when an alternating current voltage received by a rectifier of the power converter is at a negative half cycle, and executes the brown-out protection when the alternating current voltage received by the rectifier of the power converter is at a positive half cycle. In addition, the current sensing pin samples a voltage generated by the auxiliary winding to determine whether the over-voltage protection occurs after the power switch of the power converter is turned off for a predetermined time. In addition, if the prior art wants to newly add a zero-crossing function to control turning-on and turning-off of the power switch or executes a quasi resonant mode operation, the control circuit needs to add a feedback pin additionally. Thus, the control circuit with six-pin provided by the prior art cannot simultaneously realize the brown-out protection, the over-temperature protection, and the over-voltage protection.